1. Field of the Invention
The present invention relates to a control negative for use in setting a photo-printer to proper exposure conditions, prior to actual printing. More particularly, the present invention relates to a general control negative which is applicable to any kind of photo-printer for setting up proper exposure conditions.
2. Background Art
An automatic photo-printer determines an appropriate print-exposure in accordance with three color densities of a negative to be printed, which are measured by an image scanner such as a CCD scanner mounted in the photo-printer. To achieve a homogeneous image quality, it is desirable to check, prior to actual printing, the exposure conditions for three colors, to set up the photo-printer to proper exposure conditions, because the exposure conditions can change according to the photo-printer type or changes in properties of the same photo-printer, or according to a difference in color characteristics among color papers used for printing.
For setting up proper exposure conditions for three colors in the photo-printer, first a sample print is made from a control negative (or called a set-up negative), without effecting any exposure correction to the photo-printer. Next, densities of three colors, such as yellow, magenta and cyan, of the sample print are measured by a density measurement device. Then, three color densities of a previously provided reference print made from the control negative under optimum exposure conditions are also measured by the density measurement device. Then, a difference in density between the sample print and the reference print is detected color by color. According to the difference in each color density, an exposure correction value is determined for any one of the three colors, and is entered through correction keys. In this way, the photo-printer is set to proper exposure conditions where a print made from the control negative would have the same density and color balance as the reference print. The density measurement device is usually incorporated in the photo-printer, to measure three color densities from a predetermined central area of the sample print or the reference print.
Generally, most original frames expected to be printed have been photographed under daylight, i.e., sunlight from 10 a.m. to 2 p.m., or under similar exposure conditions, at proper exposure values determined based on the film speed, so that most negatives have proper image densities. In addition, it is usual that a human subject occupies about one-third of the entire area of each negative frame, while the remaining area, i.e. the background is occupied by landscapes such as trees, sky, walls and so forth. In principle, a mixture of three color transmittance densities of all pixels of a properly exposed negative results in a neutral gray.
Therefore, as a representative of such ordinary negatives, conventional control negative kit 2 contains a round eye portion 3 in a center of the frame, which is designed to be printed as a neutral gray circle in the reference print. And a background 4 of a different color density surrounds the eye portion 3, as is shown in FIG. 9. Control negative frames 5 to 8 are photographed from the same original at different exposure values. The frame 5 is photographed at a normal exposure value, so is called a normal exposed frame. The frame 6 is photographed at an insufficient exposure value, so is called an under-exposed frame. The frame 7 is photographed at an excessive exposure value, so is called an over-exposed frame. The frame 8 is photographed at a greatly excessive exposure value, so is called a super over-exposed frame. The normal exposed frame 5 represents a standard original frame to be printed. Besides these control negative frames 5 to 8, there is provided a blank frame 9 with no image on the control negative kit 2 to show a basic density of the filmstrip used for the control negative kit 2.
First, a sample print is made from the normal exposed frame 5 by measuring an average transmittance density within a photometric area, so-called LATD (large area transmittance density), of the normal exposed frame 5 through a photometric device such as a CCD image scanner. The photometric area covered by the image scanner varies depending upon the type of photo-printers. For example, three types photo-printers "COMPACT", "ROCKY" and "FAP3500" (trade names) produced by Fuji Photo Film Co., Ltd., have different photometric areas, i.e., 49%, 64% and 100% of the entire area of the full-size frame of the 135-size film, respectively. Accordingly, with the same control negative kit 2, the area ratio of the eye portion 3 to the background 4 within the photometric area would change between the different types of photo-printers. So the consequent photometric value, i.e. the average transmittance density within the photometric area, would change according to the change in area ratio of the eye portion 3 to the background 4 within the photometric area.
To avoid this problem, it is possible to provide a specific control negative kit to each photo-printer type by changing the size or the density of the eye portion 3 according to the respective photo-printer types. But this solution is obviously inefficient, and results in complicated management of the control negative kit.